LOS ANGELES--(BUSINESS WIRE)--Jun 4, 2007 - Cougar Biotechnology,
Inc. (OTCBB: CGRB) today announced that positive interim Phase I
and Phase II data on the Company's prostate cancer drug candidate
CB7630 (abiraterone acetate) was presented at the American Society
of Clinical Oncology (ASCO) Annual Meeting, which is currently
taking place in Chicago, Illinois. The data was presented in two
poster presentations on Saturday, June 2nd, as part of the poster
discussion session for genitourinary (prostate) cancer that took
place. The poster presentations are further detailed below:

Phase I/II Study of Continuous Oral Dosing of an Irreversible
CYP17 Inhibitor, Abiraterone, in Castration-Resistant Prostate
Cancer Patients Incorporating the Evaluation of Androgens and
Steroid Metabolites in Plasma and Tumor and the Study of
Circulating Tumor Cells

The Phase I/II trial of CB7630 was conducted at The Institute of
Cancer Research and at The Royal Marsden NHS Foundation Trust in
the United Kingdom. In the trial, CB7630 was administered orally,
once daily, to chemotherapy-naive patients with castration
resistant prostate cancer (CRPC), who had progressive disease
despite treatment with LHRH analogues and multiple other hormonal
therapies, including antiandrogens, diethylstilboestrol and
dexamethasone. To date, a total of 42 patients have been treated in
the Phase I/II trial, including 15 patients treated in the Phase I
stage of the trial and 27 patients treated in the Phase II stage of
the trial. In his poster presentation, Dr. Gerhardt Attard from The
Institute of Cancer Research and The Royal Marsden NHS Foundation
Trust in the United Kingdom reported that in the 42 patients
treated in this trial, CB7630 was well tolerated at doses as high
as 2000 mg/day with minimal toxicity. Moreover, no dose limiting
toxicity has been observed in the trial to date.

In the 34 patients who were evaluable for response in the Phase
I/II trial, 22 patients (65%) experienced a confirmed decline in
prostate specific antigen (PSA) levels of greater than 50%, with 10
of the 34 patients (29%) experiencing PSA declines of greater than
90%. Of the 20 evaluable patients with measurable tumor lesions,
treatment with CB7630 resulted in partial radiological responses
(as measured by the RECIST criteria) in 11 patients (55%), with 7
patients demonstrating ongoing stable disease and 3 patients
experienced regressing bone disease. Several patients treated with
CB7630 also experienced improvement in pain and a notable reduction
in opioid use. Circulating tumor cells (CTC) were detected in 16 of
34 patients and changes in CTC counts were shown to correlate with
changes in PSA.

Currently 30 of the 42 evaluable patients (71%) in the Phase
I/II trial remain on study and continue to be treated with CB7630.
Of the 15 patients in the Phase I stage of the trial, 9 patients
(60%) are still receiving treatment with CB7630 with the average
patient having received the drug for over 9.7 months, including 5
patients having received the drug for over 12 months. Of the 12
patients who started the trial longer than 9 months ago, 8 patients
(67%) have shown a confirmed response that has lasted longer than 9
months and these responses continue in all but one of these
patients.

In his poster, Dr Attard also provided an update on the Phase II
trial of CB7630 in patients with advanced prostate cancer who have
failed androgen deprivation and docetaxel-based chemotherapy. The
Phase II trial is being conducted at numerous locations in the
United States and United Kingdom. In the trial, CB7630 is
administered orally, once daily, to patients with castration
refractory prostate cancer who have failed treatment with first
line docetaxel based chemotherapy.

To date, 38 patients have been treated in this Phase II trial
with 13 of the patients having been treated for over 3 months. Of
the 38 patients who have been treated, CB7630 was well tolerated
with only minimal toxicity in this post-docetaxel population. In
the 13 patients who have been in the study for over 3 months, 10
patients (77%) experienced a decline in PSA levels of greater than
50%. Thirty-one of the 38 patients (82%) in this trial are still
receiving treatment with CB7630. Individual patients treated with
CB7630 also experienced improvement in pain and a reduction in
opioid use.

The Phase I trial was conducted at the University of California,
San Francisco Comprehensive Cancer Center with Charles J. Ryan, MD,
Assistant Clinical Professor of Medicine, as the principal
investigator. CB7630 was administered once daily to
chemotherapy-naive patients with castration refractory prostate
cancer (CRPC), who had progressive disease despite treatment with
LHRH analogues and multiple other hormonal therapies.

Of the 25 patients who had been enrolled in the study, 3
patients had "PSA only" disease and 22 patients had either bone or
soft tissue metastases. Nineteen of the 25 patients (76%) have
received 3 or more cycles of CB7630 and are evaluable for response.
Sixteen of 25 patients (64%) had received prior treatment with
ketoconazole. Treatment with CB7630 was found to be well tolerated
at doses up to 1000 mg/day. In the 25 patients who have been
treated with CB7630, 24 of 25 patients (96%) experienced a PSA
decline, including 12 of 25 patients (48%) who experienced a
greater than 50% decline in PSA and 3 of 25 patients (12%) who
experienced a greater than 90% decline in PSA. Prior treatment with
ketoconazole was not seen to impact response to abiraterone as 7 of
16 patients (44%) with prior ketoconazole exposure and 3 of 5
patients (60%) with no ketoconazole exposure experienced a greater
than 50% decline in PSA. Currently 9 of the 25 patients (36%) in
the Phase I trial remain on study and are continuing to be treated
with CB7630.

Dr. Arie S. Belldegrun, MD, FACS, Vice Chairman of the Board of
Directors of Cougar Biotechnology, said, "The interim data on
CB7630 presented at the ASCO Annual Meeting continues to support
the role of the drug as both a second line hormonal therapy, as
well as a second line chemotherapy. We are also pleased to be able
to demonstrate that CB7630 is active in patients who have failed
ketoconazole, a drug that is currently widely used off-label as a
secondary hormonal therapy. As both addressable patient populations
(second line hormone therapy candidates and second line
chemotherapy candidates) continue to represent significant unmet
medical needs in CRPC, we believe that CB7630 has strong potential
in both of these patient populations." Alan H. Auerbach, Chief
Executive Officer and President of Cougar Biotechnology, added, "We
continue to be pleased with the interim clinical data being
generated on CB7630. We greatly look forward to the continued
development of CB7630 in both the second line hormone therapy and
second line chemotherapy settings."

About Cougar Biotechnology

Cougar Biotechnology, Inc. is a Los Angeles-based biotechnology
company established to in-license and develop clinical stage drugs,
with a specific focus on the field of oncology. Cougar's oncology
portfolio includes CB7630, a targeted inhibitor of the 17-alpha
hydroxylase/c17,20 lyase enzyme, which is currently being tested in
Phase II clinical trials in prostate cancer; CB3304, an inhibitor
of microtubule dynamics, which is currently in a Phase I trial in
hematological malignancies and CB1089, an analog of vitamin D,
which has been clinically tested in a number of solid tumor
types.

Further information about Cougar Biotechnology can be found at
www.cougarbiotechnology.com.

This press release contains forward-looking statements within
the meaning of the Private Securities Litigation Reform Act of
1995. These statements are often, but not always, made through the
use of words or phrases such as "anticipates," "expects," "plans,"
"believes," "intends," and similar words or phrases. These
forward-looking statements include, without limitation, statements
related to benefits to be derived from Cougar's drug development
programs, including the potential advantages of CB7630 and its
potential for use in the treatment of CRPC and in second line
hormone and chemotherapy treatment settings. Such statements
involve risks and uncertainties that could cause Cougar's actual
results to differ materially from the anticipated results and
expectations expressed in these forward-looking statements. These
statements are only predictions based on current information and
expectations and involve a number of risks and uncertainties.
Actual events or results may differ materially from those projected
in any of such statements due to various factors, including the
risks and uncertainties inherent in clinical trials, and drug
development and commercialization, including the uncertainty of
whether results in testing of CB7630 will be predictive of results
in later stages of development. For a discussion of these and other
factors, please refer to Cougar's annual report on Form 10-KSB for
the year ended December 31, 2006 as well as other subsequent
filings with the Securities and Exchange Commission. You are
cautioned not to place undue reliance on these forward-looking
statements, which speak only as of the date hereof. This caution is
made under the safe harbor provisions of the Private Securities
Litigation Reform Act of 1995. All forward-looking statements are
qualified in their entirety by this cautionary statement and Cougar
undertakes no obligation to revise or update this press release to
reflect events or circumstances after the date hereof.